1. Field of Invention
The present invention relates to a timepiece that has a calendar mechanism for displaying the date.
2. Description of Related Art
Timepieces that have a calendar mechanism for displaying the date in the dial are known from the literature. Timepieces that are constructed to separately drive a ones date ring on which the ones digit of the date is printed and a tens date ring on which the tens digit of the date is printed in order to display the date with larger numbers are also known from the literature. See, for example, Japanese Patent 2503347.
The timepiece taught in Japanese Patent 2503347 has a ones digit wheel that has the numbers 0 to 9 for displaying the ones digit of the date printed at equal intervals on one side, and a tens digit wheel that is supported rotatably above the ones digit wheel and has the numbers 1 to 3 and a blank space for displaying the tens digit of the date provided on one side. The ones digit wheel is a circular ring and has an internal tooth ring formed along the inside circumference. A pinion (tens digit wheel pinion) is disposed in unison with the rotating shaft of the tens digit wheel.
A hand shaft for moving the hour and minute hands is disposed inside of the ones digit wheel. Also disposed inside the ones digit wheel are various wheels, such as an intermediate wheel, program drive wheel, ones program drive wheel, and tens program drive wheel, for transferring drive power from the hand shaft to the internal tooth ring of the ones digit wheel and the pinion of the tens digit wheel.
The timepiece taught in Japanese Patent 2503347 thus has various wheels for driving the ones digit wheel and various wheels for driving the tens digit wheel disposed inside the ones digit wheel. The inside diameter of the ones digit wheel must therefore be increased in order to accommodate these other wheels, thus reducing the size of the area available for printing the ones digits and preventing sufficiently increasing the size of the digits used to display the date.
A configuration rendering a gear with external teeth to the ones digit wheel (a ones digit wheel pinion) to increase the surface area for displaying the ones digits is also conceivable. However, the ones digit wheel must be positioned so that there is no interference between the ones date indicator, the tens date indicator, and the tens intermediate wheel that relays drive power to the ones date indicator and the tens date indicator, these wheels must be disposed overlapping vertically through the thickness of the timepiece, and the thickness of the timepiece is thus increased.